Iranian Journal of Forest and Poplar Research
Year:2015 | Volume:23 | Issue:1|Papers Count:24

Changes in rainfall interception and consequently in water balance cause essential effects on reforestation by indigenous and exotic tree species in the degraded areas of the Caspian forests. The aim of the present study was to compare the interception of Quercus castaneifolia, Acer velutium, and Pinus brutia plantations during the growing season in Darabkola Forest in eastern part of Mazandaran province in northern Iran. The amount of rainfall (GR) and throughfall (TF) were measured from May to November 2012 by 6 and 20 polyethylene manual gauges with 8 cm diameter each. The rainfall interception was estimated as the difference between TF and GR. During the measurement period 20 rainfall events were recorded. The amount of cumulative GR depth was 346.5 mm. Moreover, the cumulative rainfall interception of Q. castaneifolia, A. velutium, and P. brutia were 86.2 mm, 107.9 mm and 178.3 mm, respectively. The results showed that the rainfall interception was higher during the dry season, from April to September. In addition, significant correlations were observed between rainfall interception and the relative interception for the three plantations (r2 =0.781, 0.716 and 0.618 for Q. castaneifolia, A. velutium and P. brutia, respectively). It is concluded that estimating the amount of rainfall interception is crucial for selecting adapted species for reforestation in the Caspian forests. It is also a prerequisite for calculation of the water balance within reforestations.

Establishment of natural regeneration is a crucial process which plays a key role in maintaining the sustainability within the forest stands. This study aimed to investigate the quantitative characteristics of oriental beech regeneration within canopy gaps and under the canopy in Kheyroud forests of Nowshahr in the north of Iran. Two compartments were initially selected, within which a sampling grid featuring 50×50 m distance between plots was established. Regeneration frequency, species and height of seedlings and saplings were measured both within the gaps and under the canopy. Results showed the frequency and mean height of beech regeneration to be higher under canopy layer. Those parameters also significantly differed from those within the gaps. Our findings also show that the reduced light under the canopy is by no means an obstacle to increase the beech regeneration, but it rather contributes to improve the establishment of natural regeneration of beech. This research confirms the previous findings on the shade tolerance of beech and suggests creating canopy gaps in those stands in which beech seedlings are previously stabilized as a mean to support the natural regeneration.

Changes in chemical properties of throughfall and forest floor leaching in growing (leafed) and non-growing (leafless) periods essentially influence the biogeochemical cycle of forest ecosystems, especially in the broadleaved stands. The aim of this study was to compare the chemical composition. i.e. Calcium, Magnesium, Sodium and Potassium contents of throughfall as well as forest floor leaching in oriental beech trees in the Shastkolateh experimental forest of Golestan province. Throughfall and forest floor samples were taken after each rain within one year (21.08.2008 to 21.12.2009). To investigate leached nutrition of throughfall and forest floor in growing and non-growing periods, we used t-paired at the 95% confidence level. Results showed that Sodium and Potassium leaching in throughfall in the non-growing period (24.3 and 60 kg ha-1, respectively) were significantly higher than those of the growing period (52 and 18.7 kg ha-1, respectively). Furthermore, Sodium, Potassium and Calcium fluxes via forest floor in the non-growing period were 12.6, 42.3 and 8.2 kg ha-1, which showed significantly higher rates than those measured during the growing period (8.6, 23.5 and 6 kg ha-1, respectively). This study concludes that factors e.g. bark, decomposed leaves, and dry deposition play remarkable roles in the cations leaching process in forest floor within the eastern Hyrcanian forests during the non-growing period.

In order to study the competition and spatial association of trees in mixed Hornbeam stands, two 1-ha sample plots (100m×100m) were selected in the reserve area of Asalem forests in Guilan. In each plot, species and diameter at breast height (DBH) of all trees with a diameter > 7.5 cm were recorded and mapped using slope-corrected distance and azimuth from southwest corner of each plot. Distances and azimuths were later transformed to Cartesian coordinates, and all of the measured trees were assigned to one of four diameter size classes: ST (Small Timber, (DBH £ 32.5 cm), MT (Medium Timber, 32.5 < DBH £ 52.5 cm), LT (Large Timber, 52.5 < DBH £ 72.5 cm) and ELT (Extra-Large Timber, DBH > 72.5). Spatial patterns of the entire trees as well as the spatial associations among tree size classes (Intra-specific) and among species (Interspecific) were analyzed by univariate and bivariate Ripley’s K-function. Results showed that the two stands exhibited a clustered distribution. Furthermore, the interaction between the ST class and other classes was significant (P<0.05). Although we found a positive correlation between the ST and other tree classes, spatial distribution of trees showed different patterns at different spatial scales. The starting point of the attraction in LT and ELT classes was observed at a small scale, whereas it tended towards independent associations in MT class at scale of 10 meter (P>0.05). The inter-specific investigation revealed that Fagus orientalis and Carpinus betulus trees tend towards an independent association at 1-20 meter scales. At higher scales they showed yet a negative correlation. Moreover, F. orientalis was significantly and negatively correlated to Alnus subcordata at small scales. However, their mutual intra-specific and interspecific effects were different due to the fact that different natural stands have variety of demands during their life cycle. Therefore, it may not necessarily conform to their response to natural processes. This study concludes a founded understanding of spatial pattern of stands to be a helpful indicator for managing forests based on the currently operational close- to- nature silvicultural system.

The potential for carbon sequestration was evaluated for two coniferous species (Cupressus arizonica Green var. arizonica and Pinus eldarica Medw) in 17-18 year old plantations of Zob-e-Ahan industrial company near Isfahan. Transect sampling was conducted in each section, and five trees in each of the available 5 diameter classes were randomly selected and cut. Moreover, soil samples from 0 to 30 and 30 to 60 cm depth were collected in each part. Shoots and roots of the trees were separately collected and weighted. In addition, carbon sequestration of organs and soil was determined with an in-situ combustion method. Results showed that the rate of carbon sequestration was significantly different between two species (p<0.01), for which C. arizonica showed higher rate than P. eldarica. In addition, carbon sequestration showed significant difference (p<0.01) amongst the tree parts (roots, woody organs and leaves), where woody parts exhibited the highest carbon sequestration. Investigation of soil carbon storage showed no significant difference between soils in which two plantations were established.

Accurate prediction of forest fire spread is crucial in minimizing its destructive effects. Forest fire depends on various factors e.g. topography, vegetation and climate. One of the challenges in modeling forest fire concerns the way it interacts with static and dynamic spatiotemporal trajectories affecting its spread such as slope, wind speed and wind direction. In this study, three previously developed approaches Karafyllidis, Berjak and Progias for modeling those parameters were analyzed, followed by investigating the effects of pixel size and time steps in a cellular automata. The study was conducted in the Lakan forest district in the vicinity of Rasht in Guilan province. The available topographic, vegetation, wind speed and wind direction data were initially analyzed in GIS. Then the three modeling approaches were implemented, followed by a consequent sensitivity analysis on the pixel size and time steps of switching in cellular automata, The effectiveness of the approaches was compared by means of Kappa coefficient. The results indicate that the Berjak method with a 3-7 m pixel size is more appropriate for modeling the spread of fire across the study site.

This research aimed to study a number of water and soil properties of Avicennia marina mangroves to determine the potentially expandable mangrove stands. To this aim, A. marina stands located in Laft (Qeshm Island) and Khamir regions were selected. A total of 116 soils and 379 water samples were randomly collected along 9 transects in three districts: forest with regeneration, forest without regeneration and marginal lands (lands without forest). Water and soil parameters were measured to estimate the vegetative requirements of the forests, and results were statistically analyzed. The results of soil samples showed that Electrical Conductivity (EC), PH, Na+ and silt in both mangroves with regeneration and mangroves without regeneration were significantly (p<%5) less than those of marginal lands. However, organic carbon, available phosphorus and sand in both mangrove classes were significantly (p<%5) higher than those measured at marginal lands. The results of water analysis did not show any statistically significant differences in a number of parameters including EC, PH, Ca++, Mg++, Na+ and K+ between the three investigated areas. Since regeneration within the stands could be considered as an indicator of optimum vegetative conditions, the results obtained across the regeneration areas can be used as an index for development of A. marina stands.

Forest canopy height is an important input variable to derive a set of essential parameters of forest stands, which is yet costly and time consuming when measured based on ground surveys. The satellite-based laser scanner data from ICESat-GLAS provide a 3D representation of gorund objects by measuring the distance from spacecraft to the objects on the earth surface. By means of these data, this study aims to estimate forest canopy height in a portion of mountainous Kheyroud experimental forests in north of Iran. An ICESat-GLAS dataset was analyzed. Several metrics including waveform extent, lead-edge extent and trail-edge extent were extracted from waveform data, and a terrain index was additionally calculated based on a digital elevation model at the location of all laser footprints. Forest canopy height was retrieved by calculating difference between signal begin and ground peak (direct estimation) and regression models (indirect estimation). For fitting the regression, a number of 330 highest trees were measured in 33 circular plots (70 meter diameter) which were collocated with LiDAR footprints. The directly estimated height produced 2 Ra and RMSE values of 0.56 and 10.32 m, respectively. Compared to this, regression models based on combined waveform metrics and digital elevation model provided better results. Best model fit with lowest AIC= 204.55 was achieved using waveform extent and terrain index variables (Ra2=0.82; RMSE= 6.16m). The ICESat-GLAS therefore concluded to be able to retrieve a relatively accurate estimate of maximum forest canopy height in such steep mountainous area, especially on small scales. Better results are assumed to be achieved using other statistical methods, as well as by an improved waveform processing techniques.

Soil organic carbon pools (SOCP) in forests play important roles in terms of biomass productivity level as well as mitigating the climate change effects. Land-use changes cause a potential loss of SOCPs in the forest. Hence, variation of SOCPs around the forest-paddy field transition zone in northern Iran was the main aim of this study. The study was conducted within the natural forest park forest of Nour in Mazandaran province, in which the weak drainage and long periods of soil waterlogging during the rainy season are considered as crucial threats. In two remnant forest fragments with similar stand type (Maple-Ironwood), extend (10 ha) and location (adjacent to the paddy fields), soil samples were collected from two depths of 0- 20 and 20-40 cm at five distances from the farm edge into the inner forest (10 m in the paddy field and 0–10, 30–40, 70–80 and 100–110 m towards the forest interior). All the samples were collected near to the dominant Acer velutinum trees, with a minimum distance of 10 m to each other. In addition, light intensity was measured based on v per m2 in the growing season by photo-light meter measuring device in constant vertical distance from the ground. The result of paired t-test showed significantly higher carbon budget in upper soil depth compared to the lower depth in both forest and paddy fields (P<0.01). The result of one-way ANOVA indicated no significant differences among different distances to the forest stands (P>0.05). Surprisingly we observed no significant difference between the SOCPs in forest and paddy field. Besides, a significant inverse Pearson’s correlation between light intensity and SOCP was only observed for the upper soil depth in forest and paddy field (r=-0.37, P<0.05).

A study was conducted to evaluate fire risk using environmental- and human-induced factors in District Three of Neka-Zalemroud forests. For this purpose, a range of effective sub-criteria including physiographic, biological, climatic and human variables were applied. The historical fire map in study area was additionally used. It was overlaid on the spatial map of each sub-criterion to explore the correlation of the weighted high-risk classes with the historical fire occurrences. Fire risk potential map was provided based on weighted overlay of all effective sub-criteria in five classes. The historical fire map was consequently overlaid on fire risk potential map. Results showed that vegetation type and density, distance from river and the averaged relative annual humidity were associated with the highest effects in fire occurrence. Results also demonstrated the agreement of high-risk areas in the potential fire risk map with the historical fires, which supports the high validity of the applied method to assess the fire risk across the study area.

This study was carried out on 10 selected poplar clones (Populus nigra) to their compare growth and yield characteristics and to introduce the superior clones amongst those which were previously-surveyed over 8-year period. The clones were surveyed in a randomized complete block design with 3 replications on 3×3 meters distance in Mehregan research station of Kermanshah. In the first year all of sprouts except the strongest ones were removed. Moreover, weed control and irrigation were performed during the entire experimental period. At the end of each growing season, diameter at breast height (DBH) and total height of trees were measured, and annual growth of diameter and height as well as wood volume per ha and its mean were derived. Results indicated that although clones’ behaviors are different for the two periods, they showed an overall positive trend. However, the height, DBH, annual growth of DBH and height, wood volume per ha and its mean value for the second period showed increased rates for the second period compared to the first period. In the light of this study, the selected clones included P. nigra 56.75, P. nigra 63.135, P. nigra 56.52 and P. nigra 56.32 which demonstrated the highest productive indications and are thus recommended for cultivation in Kermanshah province.

Direct measurement of aboveground biomass of trees is considered as one of the laborintensive, expensive, time consuming and destructive tasks. The objective of this study was to estimate the biomass of four coniferous and deciduous trees species (Pinus eldarica, Cupressus arizonica, Robinia pseudoacacia and Morus alba) by means of high resolution Quickbird remotely-sensed data of over a plantation are established around the industrial domain of Isfahan’s Mobarakeh Steel Company. To this aim, three approaches based on vegetation indices, texture analysis and Principal Component Analysis (PCA) were applied to extract required information from satellite imagery. The correlation analysis between field-assessed biomass and the image-based information and regression models were built. The results using vegetation indices (DVI and NDVI) for coniferous species as well as athose from texture analysis and PCA for deciduous species showed significant corelations. As depicted by the species-specific regression of biomass revealed the amount of RMSE for P. eldarica, C. arizonica, R. pseudoacacia and M. alba to be 53, 20, 30 and 50, respectively. Moreover, species-specific biases for P. eldarica, C. arizonica, R. pseudoacacia and M. alba was shown to be 30, 10, -30 and 44 respectively. The results of this study supports the use of the applied Quickbird data for model-based estimation of aboveground biomass across the study site.

Native fast growing species of Euphrates poplar (Populus euphratica) is broadly distributed in Iran and is considered important due to its tolerance to saline soils and warm and dry climate conditions. In this study, twenty Euphrates poplar provenances and a cell-cultured clone from all over country were studied in Kushkak research station in Khuzestan province, one of the main Euphrates poplar habitats in Iran. Thirty cuttings from each provenance were planted under a RCBD in February 2010. Growth characteristics including collar diameter (CD), height (H), Germination percentage (GP) of cuttings, special leaf area, and dry matter percentage of leaves were studied. In addition, a number of leaf morphological traits including leaf length (LL), maximum width (MLW), LL to MLW ratio, petiole length (PL), PL to LL ratio, thickness and leaf area, branch-to-stem angle (BSA) and number of branches > 0.5 m (NB) were also recorded during one year after planting. ANOVA results showed that all investigated traits significantly differed in all parameters except NB and BSA. Moreover, provenances of Ramhormoz and Isfahan showed the highest rates of CD and H growth. Mahneshan provenance was the most unfavorable genotype for establishment in north of the Khuzestan province due to its low GP as well as its incompatible morphology with warm climate of the region. Consequently, PCA results revealed significant differences of that provenances of Mahneshan, Jolfa, Zabol and Kerman to other genotypes.

The different species form the genus Eucalyptus spp. are amongst the most important fast growing tree types of Oceania which have been planted in Iran for more than 50 years. In particular, the Eucalyptus trees were vastly planted in the southern parts of the country, from which the old-growth trees are still found in Lorestan (e.g. Malavi region) and Fars provinces. The applications to produce wood pulp, paper and leaf oils are amongst the motivations for future industrial and medicinal uses. In this study, the adaptation and performance of different industrial Eucalyptus ecotypes in Lorestan province were tested. A range of species including E. globulus (spp. bicostata), E. globulus (spp. maidenii), E. nitens, E. viminalis (spp. cygnetensis), E. camadulensis (var. obtus) and E. suggrandis (spp. suggrandis) were planted with 3 m distance within a complete randomized block design in a 2-ha field and were monitored for a 7-year period. The comparison of means by Duncan test showed the E. camadulensis (spp. obtus) and E. globulus (spp. maidenii) to be superior regarding the majority of their investigated properties in 99% confidence level.

The historically-established exploitation of resin from wild pistachio (Pistacia atlantica Desf.) plays a great role in the socioeconomic balance and livelihood of rural communities of Zagros forest region. The objective of this study is to assess the impact of resin exploitation on diameter increment of wild pistachio. Two stands including a 4.8 ha abandoned stand (in which resin exploitation was previously ceased between 1991 and 2013) and a 9.6 ha stand (currently undergoing resin exploitation) with similar physiographic conditions were selected in the villages Bivand-bala and Bivand-paeen in Javanroud, Kermanshah province. To evaluate the diameter increment, 18 tree samples in the abandoned stand and 16 samples in the utilized stand were taken, and increment cores were extracted from each tree at the height of 30 cm using increment borer. In the increment cores, current annual radial increment (CARI) was measured for a period between 1980 and 2013. Current annual diameter increment (CADI) and its percentage (PCADI) of all diameter classes were calculated for two periods of 1980-1991 and 1991-2013. The normal distribution of the data was tested using Kolmogorov–Smirnov test. Comparing diameter increment of trees in the two stands was performed by independent-samples t test. The results indicated no significant difference in the average PCADI values between the abandoned and utilized stands during 1980-1990 (in which both stands had undergone relatively similar level of human interferences and resin extraction). The results for the period of 1991-2013 (in which resin exploitation was ceased in the abandoned stand) the average values of PCADI in diameter classes (35-60 cm) were significantly different between the two studied stands, where the abandoned stand showed higher values than the utilized stand. However, no significant difference was observed between the two stands between 1980 and 1991. Furthermore, the averages of PCADI in wild pistachio trees were significantly different for the period of 1991 to 2013 (P<0.01).

During the last decade, oak decline has caused critical health issues within the Zagros forests in west Iran, which is currently approaching a threatening level with effects on stand structure and stability. Identifying the influential factors on the spread of this phenomenon can thus help forest planners and administrating units to control the crisis. This study aimed to assess different aspects influencing deterioration of oak trees with respect to stands environmental characteristics in the southern part of Zagros forests. For this purpose, 12 declined stand dominated by Brant’s oak (Quercus brantii) at different conditions in both the North and South aspects as well as two altitudes and three replications were chosen within Meleh-Siah forest site in Ilam province. A transect line was randomly assigned to each of the stands, along each or which three square plots (2500 square meter) were laid. Within the plots, all individual trees were inventoried. By using a randomized complete block and factorial design, methods were used to compare the mean values of the inventoried parameters. Although the results showed no significant difference between diameter, height, crown length and basal area of the stands along gradients of aspect and altitude, significant effect of aspect on decline rate in seed based trees as well as altitude on coppice trees were observed. The degree of decline in south aspect was greater than in north aspect. In addition, lower elevations showed larger effects than higher elevations. The interaction between two factors was also significant on the decline rate.